Magnifying Visors

How close can a magnifying glass be to a piece of paper before it stops working?

Does it depend on the magnifying glass? Is there some sort of formula to work it out?

Public Comments

1. That depends on the magnifying glass. Specifically its FOCAL LENGTH. THAT depends on how the lense is made.
2. There is no limit on how close.... the glass never stops working. The issue is the focal length of the magnifying glass lens. That determines the distance from the glass to the paper to focus the sun into the smallest image possible.... which is how you burn ants and paper. Have fun!